The present invention relates to a vehicle headlamp designed to switch beams by moving a shade.
A vehicle headlamp is constructed such that a beam for high beam or low beam is emitted by reflecting forward light from light source with a reflector. Since light distribution patterns for the low beam and the high beam are different, a general practice is to use two light sources and switch them on and off selectively such that the headlamp switches between the low beam and the high beam.
However, a vehicle headlamp is also constructed to switch beams using a single light source. In particular, such construction is found with many two-unit type headlamps, which has a discharge bulb as a light source bulb.
One conventional switching method using a single light source switches beams with a moving shade. In this method, the shade is designed to move between two positions providing different screening of incident light given off from a light source to a reflector or reflected light from the reflector, with a beam switching device containing an actuator such as a solenoid.
However, in a vehicle headlamp of the foregoing prior art beam switching device, since the shade and the actuator for driving the shade are coupled to each other with a pin or the like, the assembling of the beam switching device to a lamp is difficult and results in a low production performance.
Particularly, with the foregoing prior art beam switching device, the actuator needs to be unitized in advance by being coupled to the shade, and a resultant complicated massive unit has to be assembled to a lamp, making the assembling operation very cumbersome.
In addition to the drawback indicated for the foregoing device with beam switching between the low beam and the high beam by the moving shade, a similar drawback may occur if a beam switching is designed to take place between other beams, for example, between the low beam and a fog beam.
The present invention is provided in view of those situations. An object of the present invention is to provide a vehicle headlamp having a beam switching function performed by moving a shade, configured to facilitate assemblage of a beam switching device to the headlamp.
The present invention attains the above object by devising the construction of a beam switching device.
According to an embodiment of the invention, there is provided a vehicle headlamp comprising a light source, a reflector for reflecting forward light from the light source, a shade for screening part of incident light given off from the light source to the reflector or light reflected from the reflector and a beam switching device for switching beams by moving the shade between two positions providing a different amount of screening of the incident light or the reflected light. The beam switching device comprises an elastic member for elastically biasing the shade to either of the two positions and an actuator for pressing the shade against the elastic biasing force of the elastic member to move the shade to either of the two positions.
The xe2x80x9cvehicle headlampxe2x80x9d may be a general headlamp having a reflector formed based on a paraboloid or a so-called projector-type headlamp.
The xe2x80x9clight sourcexe2x80x9d above is not limited to any specific one, but may be a discharge illuminant portion or a filament of an incandescent bulb such as a halogen bulb.
The xe2x80x9cshadexe2x80x9d maybe a shade for screening part of incident light given off from the light source to the reflector or part of reflected light reflected from the reflector.
The method for moving the shade xe2x80x9cbetween two positionsxe2x80x9d is not limited to a specific method, but the movement of the shade may be effected through any rotary motion or linear reciprocating motion.
The xe2x80x9celastic memberxe2x80x9d is not limited to a specific kind of elastic member, but any kind of elastic member may be used, provided that it can elastically bias the shade to one or the other of the two positions. For example, a tension coil spring, a compression coil spring, a torsion coil spring, a plate spring, a rubber or the like may be used.
The xe2x80x9cactuatorxe2x80x9d is not limited to a specific kind of actuator, but any kind of actuator may be used, provided that it can move the shade to either of the two positions against the elastic biasing force of the elastic member. For example, a solenoid, a motor cam mechanism or the like may be adopted.
As shown in the foregoing construction, the vehicle headlamp according to the invention comprises the beam switching device for switching beams by moving the shade for screening part of incident light given off from the light source to the reflector or light reflected from the reflector between two positions each providing a different amount of screening comprising a light source. The beam switching device comprises the elastic member for elastically biasing the shade to either of the two positions and the actuator for pressing the shade against the elastic biasing force of the elastic member to move the shade to either of the two positions. Thus, the vehicle headlamp of the invention obtain the following function and advantage.
Unlike the actuator of the conventional construction, which is coupled to the shade with a pin or the like, the actuator of the present invention is constructed to contact the shade detachably to press the shade against an elastic biasing force. Thus, the beam switching device can be assembled to the headlamp only by disposing the actuator and the elastic member at predetermined positions, respectively.
Thus, according to the present invention, the beam switching device can easily be assembled to the vehicle headlamp constructed such that the beam switching is carried out by the moving shade.
The mode of beam switching by the beam switching device is not limited to a specific mode. However, if the beam switching device is constructed to switch between the low beam and the high beam with one of the two positions set for the low beam and the other set for the high beam, and if the positioning member is constructed to be brought into abutment with the shade when the shade has moved to the low beam position, the shade can be located accurately at the low beam position when the high beam is switched to the low beam. The above configuration functions to obviate the necessity of alignment of the actuator such as required when the shade is located and retained at the low beam position, thereby making it possible to simplify the construction of the beam switching device.
The position where the beam switching device is disposed is not limited to a specific position, but if the position is located at the lower area of the reflector, the following function and advantage can be obtained. The lower area of the reflector is not as important as the other areas thereof with respect to the light distribution of the headlamp. In the event that the beam switching device is designed to be disposed in this lower area, the beam switching device can be disposed with a space saving construction needing no wide space, without adversely affecting the light distribution performance of the headlamp.